Miniaturization of integrated circuit (IC) devices demands superior electrical properties from both dielectric and conductive materials used in the manufacturing of an integrated circuit. Dielectric materials with low dielectric constant (low-k and ultra low-k dielectrics) have replaced the traditionally used silicon dioxide as an inter-layer dielectric (ILD) material, while copper has replaced aluminum as a conducting material in many applications due to its lower resistivity. The low-k dielectric materials used in the IC device processing include carbon doped silicon dioxide, hydrogenated silicon oxycarbides (SiCOH), fluorine doped silicon dioxide, and organic-containing low-k dielectrics. These materials, due to their low dielectric constants, provide low parasitic capacitance and minimize the “crosstalk” between the interconnects in an integrated circuit. At the same time, they are often porous foam-like materials and are generally more easily damaged during the processing steps than silicon dioxide.
Currently used IC fabrication processes often include operations that remove or redistribute material on a wafer surface using ions generated in a plasma. These operations are often referred to as sputter etching or resputtering. In such methods, positively charged inert gas ions or metal ions impinge on a negatively biased substrate and remove or redistribute portions of exposed material residing on a wafer substrate. Examples of materials that can be removed or redistributed using sputter etching and resputtering include diffusion barrier materials, such as Ta and TaNx, and seed layer materials, such as copper and its alloys. These materials usually reside on a layer of a low-k dielectric, which can be damaged during plasma etching and resputtering operations, resulting in decreased reliability of the formed IC devices.
As the dimensions of IC devices continue to decrease, and the dielectric materials used in IC fabrication become more delicate, the need for improved methods of sputter etching and resputtering becomes more pronounced.